var top1=0,left1=0; 

var moveFunction = function(event){

    console.log('x=',event.clientX);

    console.log('y=',event.clientY);

    console.log('ox=',event.offsetX);

    console.log('oy=',event.offsetY);

    document.getElementById('dialog').style.top =  event.clientY - top1+ "px";

     document.getElementById('dialog').style.left = event.clientX - left1 + "px";

 };

​

var mousedownFunction = function(event){

  var obj = document.getElementById('dialog');

  top1 = event.offsetY; //event.clientY - obj.offsetTop;

  left1 = event.offsetX;//event.clientX - obj.offsetLeft;

  document.getElementById('dialog').addEventListener('mousemove',moveFunction);

}

​

document.getElementById('dialog').addEventListener('mousedown',mousedownFunction);

​

​

document.getElementById('dialog').addEventListener('mouseup',function(){

  document.getElementById('dialog').removeEventListener('mousemove',moveFunction);

});